The present invention relates to an aqueous ink composition having high water resistance and excellent age stability and resistance to drying-up.
A variety of researches and developments with reference to aqueous ink compositions retaining water resistance have hitherto been conducted.
The so-called pigment type aqueous inks containing pigments as the main elements are well-known to the art. However, these pigment type aqueous inks are poor in dispersion stability and have the problem of sedimentation of pigment particles with time. When these inks are used for writing instruments, they tend to plug the ink passage and thus to inhibit the smooth flow of ink in the writing instrument. The deposition of the pigment particles along with the evaporation of water in this type of ink causes the plugging of the ink passage; the so-called drying-up phenomenon at the writing tip of a pen.
Thus, an aqueous ink composition having high water resistance, excellent age stability and resistance to drying-up has been desired to be developed.